feat(breaking): Add ClassTag, improve Effect.serviceConstants, require string identifier for all tags

[mikearnaldi]

With this change we now require a string key to be provided for all tags and renames the dear old Tag to GenericTag, so when previously you could do:

import { Effect, Context } from "effect";
interface Service {
  readonly _: unique symbol;
}
const Service = Context.Tag<
  Service,
  {
    number: Effect.Effect<never, never, number>;
  }
>();

you are now mandated to do:

import { Effect, Context } from "effect";
interface Service {
  readonly _: unique symbol;
}
const Service = Context.GenericTag<
  Service,
  {
    number: Effect.Effect<never, never, number>;
  }
>("Service");

This makes by default all tags globals and ensures better debuggaility when unexpected errors arise.

Furthermore we introduce a new way of constructing tags that should be considered the new default:

import { Effect, Context } from "effect";
class Service extends Context.Tag("Service")<
  Service,
  {
    number: Effect.Effect<never, never, number>;
  }
>() {}

const program = Effect.flatMap(Service, ({ number }) => number).pipe(
  Effect.flatMap((_) => Effect.log(`number: ${_}`))
);

this will use "Service" as the key and will create automatically an opaque identifier (the class) to be used at the type level, it does something similar to the above in a single shot.

[changeset-bot]

🦋 Changeset detected

Latest commit: c74d900

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 18 packages

Name	Type
@effect/platform-node-shared	Major
@effect/platform-browser	Major
@effect/opentelemetry	Major
@effect/platform-node	Major
@effect/experimental	Major
@effect/platform-bun	Major
@effect/rpc-workers	Major
@effect/platform	Major
@effect/rpc-http	Major
effect	Minor
@effect/schema	Major
@effect/cli	Major
@effect/rpc	Major
@effect/rpc-http-node	Major
@effect/rpc-nextjs	Major
@effect/printer-ansi	Major
@effect/printer	Major
@effect/typeclass	Major

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[patroza]

Love the class. But then go all the way; allow to take the name of the class?
nvm, as the const key is what makes the unique identification work it's not useful.

[mikearnaldi]

As a follow up I propose renaming Tag to GenericTag and moving ClassTag to be Tag

[patroza]

As a follow up I propose renaming Tag to GenericTag and moving ClassTag to be Tag

Some more ideas to infer the shape from the make effect; https://github.com/effect-ts-app/libs/blob/34c0458a3e9e5a42b723260802785ce369ee07d5/packages/prelude/_src/service.ts#L72

[mikearnaldi]

Love the class. But then go all the way; allow to take the name of the class?

Not sure I understand your suggestion, please provide a code snippet

[IMax153]

@mikearnaldi - big fan of this - simplifies a lot of boilerplate around Tag. I also agree with Tag -> GenericTag and ClassTag -> Tag.

Nice work 👍

[tim-smart]

Looks good! Agree with the renaming too.

Quick fix to ensure the definition stack is set correctly: #2029